1. Field of the Invention
This invention generally related to a system and method for treating industrial wastewater containing organic matter and mineral salts.
The basic concepts underlying the oxidative evaporation process are as follows:                a. All oxidative reactions are exothermic (heat generating) processes. In order to have complete oxidation, the heat that is generated must be removed. On the other hand, the evaporation of water is a heat consuming process. Coupling these two processes in situ creates a symbiotic environment in which the heat generated through oxidative reactions facilitates the evaporation of water, the heat consuming nature of which promotes improved oxidation.        b. When the oxidative reactions take place among organic compounds and oxygen, the reaction yields CO2 and water as the end products. By maintaining the reaction environment in alkaline, the CO2 produced in the reaction is neutralized to form carbonates. The carbonates are water soluble and are retained in the liquid solution. This neutralization reaction is also exothermic in nature, thereby generating heat that can be used to evaporate more water.        c. Water vapor generated in a confined vessel is in an equilibrium state with respect to the coexistence of water and steam. The water vapor, saturated steam, can be removed out of the vessel by sweeping with inert gas (i.e., gas that has no affinity to steam), such as oxygen gas. The amount of water vapor withdrawn from the vessel is proportional to the rate of gas flow sweeping through the vessel. Under the operation controlling at a constant temperature in the reactor, the amount of water to be evaporated can thereby be precisely controlled by the gas flow through the vessel.        d. As the result of water evaporation, the concentration of the solids in the remaining liquid increases. Further evaporation of water can be achieved by introducing the high temperature liquid to a low pressure chamber, the so-called flashing evaporation. The flashing evaporation is an adiabatic process that no heat is supplied for evaporation of water. In the process of adiabatic evaporation, water is evaporated while the temperature of the remaining liquid decreases.        e. Since the temperature of the depressurized solution becomes lower than that of the off-gas stream from the reactor, the depressurized solution can be used as the cooling media to absorb heat from the reactor off-gas. The water in the cooling media will also evaporate while being heated by the off-gas.        f. By recycling the depressurized solution back to the reactor system, the salts in the feed and that produced in the reactor system will accumulate in the circulating stream. Eventually, the liquid solution will become saturated With the oxidized salts, which will be recovered in the form of crystals upon cooling.        
2. Description of the Related Art
The conventional process for treating wastewater containing organic compounds, with the use of high temperature and pressure, is known as the Wet Air Oxidation Process. In the Wet-Air-Oxidation process, liquid and air (the oxidizing agent) are co-currently mixed to form a two phase flow throughout the reaction area, and that the process requires to suppress water vaporization in order to maintain this mixed phase flow. The end product of the Wet-Air-Oxidation process remains as liquid effluent that requires a secondary treatment before the final disposal.
The conventional process for evaporation refers to the single or multi-effect evaporation systems. The conventional evaporation system is generally operated under vacuum. The heat required for evaporation of water solely relies on the supplies from outside sources, and the removal of the generated vapor relies on vacuum pumping operations performed by means of mechanical or hydraulic devices. In contrast to those features, the process of this invention is operated under pressurized condition, utilizing the heat generated by the oxidative and neutralization reactions for evaporating water in situ, and provides a forced circulating gas to remove vapor generated in the reactor at a controlled rates.